sinning (n.)

Middle English sinnen, from Old English syngian "to commit sin, transgress, err," from the source of synn (see sin (n.)); perhaps there was a verb in Proto-Germanic (compare Old Saxon sundion, Old Frisian sendigia, Middle Dutch sondighen, Dutch zondigen, Old High German sunteon, German sündigen "to sin"). The form was altered from earlier Middle English sunigen by influence of the noun.